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§ 3. Particulars. 
The practical execution of the system discussed has given various 
experiences, which I will communicate here. In fig. 4 and 5 the 
Photo J. QUELLE. 
Fig. 4. Arrangement of two recording porometers, the chambers of which 
have been fixed to one leaf of a Ficus elastica on either side of the middle- 
vein. Explanation of letters and marks in the text. To the left a hygrograph 
and behind it a thermograph. Through the opening at the top in the middle 
something of the sunshine-autograph may be seen. 
real arrangement of the parts has been illustrated, deviating here 
and there from the schematic fig. 1. The signification of letters and 
figures is the same throughout. 
1. The glass chamber. At present I always use the model, as 
illustrated by van SLOGTEREN on p. 18 of his dissertation, so the one 
with the side-tube attached near the edge. In the case of Ficus 
elastica I use chambers with wide mouths (diameter 4 centims), 
because by doing so a greater number of stomata is set to work 
and the falling of the water in the porometer goes quicker. Because 
I use pressures, little below the atmospheric pressure, (viz. between 
7 and 4 millims underpressure or between 5 and 1 millims under- 
pressure) to make the condition of the plant differ as slightly as 
possible from the natural condition, the fall-period is longer than 
